Gregor Vorbarra is the Emperor of the Barrayaran Imperium in the sci-fi series the Vorkosigan Saga by Lois McMaster Bujold.
As of CryoBurn, Gregor Vorbarra is the current Emperor of Barrayar. He consequently rules over Barrayar, Komarr, and Sergyar, the three planetary bodies of the Barrayaran Empire.
His father was the late Crown Prince Serg, and his grandfather was Emperor Ezar Vorbarra. They had both died by the time Gregor was five, therefore, Admiral Lord Vorkosigan ruled as Regent until Gregor reached the age of majority. This was not the last of Gregor's woes as a child, as he became a pawn in a power struggle between the Regent and the usurper Count Vordarian, a struggle that cost the life of his mother, Princess Kareen Vorbarra.
Gregor's name is an apparent inconsistency in the world-building of the Vorkosigan Saga. Vor tradition provides that the first-born son has the paternal grandfather's first name, which in this case is Ezar.
Gregor is a fairly progressive and liberal emperor, but must remain even-handed in order to rule effectively. He is also Count Vorbarra, and technically has a vote in the Council of Counts. By tradition, he does not exercise that vote except to break a tied ballot, much like the vote of the Vice President of the United States in the United States Senate. Psychologically, Gregor lives in fear that he carries the madness that afflicted his relatives, particularly his sadistic father Crown Prince Serg, but also the mad Yuri Vorbarra and his relations in the Vorrutyer clan, best (or worst) exemplified by Serg's companion in depravity, Ges Vorrutyer. While capable of great personal warmth, he maintains iron control in most situations, projecting an air of deep calm.